Leakage Test Method for Fuel Cell Stack

Abstract

The present invention relates to a method for leak testing a fuel cell stack. In a cylinder installation process (S1), a first end structural member (18a) and a second end structural member (18b) of the fuel cell stack (10) are respectively connected to a cylinder (42). At this time, a first opening (44) and a second opening (46) formed at both ends of the cylinder are respectively closed by the first end structural member and the second end structural member. Accordingly, the fuel cell stack is surrounded by the cylinder. In addition, a gap (52) is formed between the outer wall of a battery cell (12) of the fuel cell stack and the inner wall of the cylinder. In a determination process (S4), an inspection gas is supplied into the fuel cell stack. And it is determined whether the inspection gas exists in the gap.

Description

Technical Field

[0001] The present invention relates to a method for leak testing a fuel cell stack to check whether there is a leak site in the fuel cell stack. Background Art

[0002] A single cell of a fuel cell stack includes an electrolyte membrane-electrode assembly (MEA) in which an electrolyte membrane is sandwiched between an anode electrode and a cathode electrode. In the single cell, the MEA is clamped by a pair of separators. A fuel cell stack is composed of a plurality of the single cells stacked together. The fuel cell stack operates by supplying a hydrogen-containing fuel gas to the anode electrode and an oxygen-containing oxidant gas to the cathode electrode. During operation, a cooling medium such as water is supplied to the fuel cell stack.

[0003] When there is a leak site in the fuel cell stack, at least one of the fuel gas, the oxidant gas, or the cooling medium leaks from the inside of the fuel cell stack to the outside during the operation of the fuel cell stack. To avoid this, as described in Patent Document 1, a leak test is performed before actually using the fuel cell stack.

[0004] Conventionally, as described in Patent Document 2, the leak test is performed using dedicated equipment. In this case, it is necessary to transport the fuel cell stack to the dedicated equipment. Since the fuel cell stack is quite heavy, such transportation is complicated and burdensome for the operator. From this viewpoint, Patent Document 2 proposes a structure for performing the leak test at the installation site of the fuel cell stack.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-156038

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2010-49952 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] In the technique described in Patent Document 2, a material that reacts with hydrogen and changes color is used. In the case of a leak of the oxidant gas or the cooling medium, the material does not change color. Therefore, the case where the oxidant gas or the cooling medium leaks cannot be detected.

[0011] The main object of the present invention is to provide a method for leak testing a fuel cell stack that can simply determine whether there is a leak in the fuel cell stack.

[0012] Means for Solving the Problems

[0013] According to an embodiment of the present invention, there is provided a method for leak testing a fuel cell stack to check whether there is a leak site in the fuel cell stack. The fuel cell stack is laminated with a plurality of battery cells, and a first end structural member and a second end structural member are located at the end portions in the lamination direction of the battery cells. In the method for leak testing the fuel cell stack, it includes:

[0014] A cylinder installation process of connecting a cylinder that forms a first opening and a second opening at both ends and extends from the first end structural member to the second end structural member to the first end structural member and the second end structural member, whereby the first end structural member and the second end structural member respectively close the first opening and the second opening, and a gap is formed between the outer wall of the battery cell and the inner wall of the cylinder, and the cylinder surrounds the battery cell; and

[0015] A determination process of supplying an inspection gas to the inside of the fuel cell stack and determining whether the inspection gas exists in the gap.

[0016] Effects of the Invention

[0017] According to the present invention, the fuel cell stack is directly covered with a cylinder. Whether there is a leak site in the fuel cell stack can be determined according to whether the inspection gas leaks from the fuel cell stack into the cylinder. Therefore, a large container for accommodating the fuel cell stack is not required. Nor is a lifting mechanism for lifting the fuel cell stack into the container or lifting the fuel cell stack out of the container required. In addition, the leak test is also simple.

[0018] For such reasons, simplification and miniaturization of the leak test device can be achieved. In addition, dedicated equipment such as a container or a lifting mechanism is not required, so the leak test can be carried out at the installation site of the fuel cell stack or near the installation site. Therefore, there is no need to transport the fuel cell stack to the leak test device. Thus, the operation is simple and the time required for the leak test is shortened. As a result, the burden on the operator is reduced.

[0019] The following embodiments will be described with reference to the drawings. The above objects, features, and advantages can be more easily understood from the description. Description of the Drawings

[0020] Figure 1 It is a schematic perspective view showing a fuel cell stack and a cylinder surrounding the fuel cell stack.

[0021] Figure 2 It is a schematic perspective view of the main part showing the state of assembling the fuel cell stack into an airtight test device for implementing the leak test method according to the first embodiment of the present invention.

[0022] Figure 3is a schematic side cross-sectional view along the longitudinal direction of the fuel cell stack when the fuel cell stack is surrounded by a cylinder.

[0023] Figure 4 is a schematic flow chart of the leak test method according to the first embodiment.

[0024] Figure 5 is a schematic side cross-sectional view showing a state in which the fuel cell stack is assembled into the immersion test device for implementing the leak test method according to the second embodiment of the present invention.

[0025] Figure 6 is a schematic flow chart of the leak test method according to the second embodiment.

[0026] Figure 7 is schematically shown when the fuel cell stack is assembled into Figure 5 a different immersion test device, and is a schematic side cross-sectional view of the state.

[0027] Figure 8 is a schematic three-dimensional exploded view of a cylinder composed of a plurality of components.

[0028] Figure 9 is a schematic three-dimensional exploded view of another cylinder composed of a plurality of components, which is different from the Figure 8 cylinder. Detailed Embodiments

[0029] Hereinafter, preferred embodiments of the leak test method for the fuel cell stack according to the present invention will be given and described in detail with reference to the drawings.

[0030] First, with reference to Figure 1 , a general description of the fuel cell stack 10 will be given. The fuel cell stack 10 includes a single cell stack 14 formed by stacking a plurality of cell units 12. Each cell unit 12 has an electrolyte membrane-electrode structure (MEA) with an electrolyte membrane sandwiched between an anode electrode and a cathode electrode. Each cell unit 12 has a set of separators sandwiching the MEA. A resin frame member may be provided on the outer periphery of the MEA. A fuel gas flow path is formed in one of the set of separators. An oxidant gas flow path is formed in the other of the set of separators. The separators of adjacent cell units 12 overlap each other. A cooling medium flow path is formed between the overlapping separators. Since the above structure is well known, detailed description and illustration are omitted.

[0031] The single cell stack 14 is sandwiched by a set of terminal boards 15a and 15b. Outside the terminal boards 15a and 15b, insulating boards 16a and 16b formed of insulators are respectively disposed. Outside the insulating boards 16a and 16b, a first end face plate 18a and a second end face plate 18b are respectively disposed. That is, at both ends in the stacking direction of the battery cells 12, the terminal boards 15a and 15b, the insulating boards 16a and 16b, and the end face plates 18a and 18b are provided. The terminal boards 15a and 15b, the insulating boards 16a and 16b, and the end face plates 18a and 18b are sequentially arranged in this order from the inside to the outside of the single cell stack 14. In the first embodiment and the second embodiment described later, the first end face plate 18a and the second end face plate 18b are respectively located at both ends of the fuel cell stack 10. In the first embodiment and the second embodiment, the first end face plate 18a corresponds to the first end structural member, and the second end face plate 18b corresponds to the second end structural member.

[0032] The outer dimensions (height and depth) of the first end face plate 18a and the second end face plate 18b are larger than the outer dimensions (height and depth) of the separator. Therefore, as Figure 1 shown, the outer edge end faces of the first end face plate 18a and the second end face plate 18b protrude outward from the outer edge end face of the battery cell 12. A plurality of threaded holes 22 are formed in the outer edge end faces of the first end face plate 18a and the second end face plate 18b. For example, members such as a protection panel are connected to the threaded holes 22 by connecting screws 20. Figure 1 Also shown are the threaded holes 24 formed in the end face in the stacking direction of the first end face plate 18a. A protection panel or the like is also connected to the threaded holes 24. However, for the sake of convenience of explanation, different reference numerals are attached to the threaded holes 22 and the threaded holes 24.

[0033] At the left end of the first end face plate 18a Figure 1 , a fuel gas discharge communication hole 30b, a cooling medium supply communication hole 32a, and an oxidant gas supply communication hole 34a are formed along the vertical direction. At the right end of the first end face plate 18a Figure 1 , an oxidant gas discharge communication hole 34b, a cooling medium discharge communication hole 32b, and a fuel gas supply communication hole 30a are formed along the vertical direction. The six communication holes 30a, 30b, 32a, 32b, 34a, and 34b extend parallel to each other in the inside of the single cell stack 14 along the stacking direction of the battery cells 12.

[0034] A fuel gas communication path 30c, an oxidant gas communication path 34c, and a cooling medium communication path 32c are formed in the second end face plate 18b (all refer to Figure 3)。The fuel gas communication path 30c connects the fuel gas supply communication hole 30a and the fuel gas discharge communication hole 30b. The oxidant gas communication path 34c connects the oxidant gas supply communication hole 34a and the oxidant gas discharge communication hole 34b. The cooling medium communication path 32c connects the cooling medium supply communication hole 32a and the cooling medium discharge communication hole 32b. The communication paths 30c, 32c, and 34c are provided as grooves in the second end plate 18b.

[0035] The fuel gas supply communication hole 30a and the fuel gas discharge communication hole 30b communicate with the fuel gas flow paths formed in the respective separators. The oxidant gas supply communication hole 34a and the oxidant gas discharge communication hole 34b communicate with the oxidant gas flow paths formed in the respective separators. The cooling medium supply communication hole 32a and the cooling medium discharge communication hole 32b communicate with the cooling medium flow paths formed between the separators.

[0036] Use Figure 2 and Figure 3 The leak test method according to the first embodiment is implemented using the airtight test device 40 shown. Next, the airtight test device 40 will be described.

[0037] The airtight test device 40 includes a first cylinder 42 that surrounds the fuel cell stack 10. The first cylinder 42 is a container for performing an airtight test. As a preferred example of the material of the first cylinder 42, a resin material such as an acrylic resin or a metal material such as an aluminum alloy can be cited. The first cylinder 42 is preferably formed of a single member. This is to avoid leakage from the first cylinder 42 in this case.

[0038] The cross section of the first cylinder 42 orthogonal to the longitudinal direction is substantially rectangular. The first cylinder 42 is a hollow body. A first opening 44 is formed at one end in the longitudinal direction of the first cylinder 42. A second opening 46 is formed at the other end in the longitudinal direction of the first cylinder 42. The opening dimensions (height and depth) of the first opening 44 and the second opening 46 correspond to the outer dimensions of the first end plate 18a and the second end plate 18b. Sealing members 48 are individually provided on the inner walls of the first opening 44 and the second opening 46. The sealing members 48 seal between the first cylinder 42 and the first end plate 18a (or the second end plate 18b). As a typical example of the sealing member 48, an O-ring or the like can be cited. The sealing member 48 can also be a sheet-like gasket.

[0039] Alternatively, a flange may be provided at one end of the first cylinder 42. In this case, on one of the first end plate 18a or the second end plate 18b, the flange can be fastened to a portion close to the single cell laminate 14 by screw fastening.

[0040] At the longitudinal end of the first cylinder body 42, a plurality of screw insertion holes 50 are formed so as to surround the first opening 44 or the second opening 46. The positions of the screw insertion holes 50 correspond to the positions of the threaded holes 22 formed on the outer edge end faces of the first end plate 18a or the second end plate 18b. The connecting screws 20 passing through the screw insertion holes 50 are screwed into the threaded holes 22, whereby the first cylinder body 42 is connected to the first end plate 18a. Similarly, the connecting screws 20 passing through the screw insertion holes 50 are screwed into the threaded holes 22, whereby the first cylinder body 42 is connected to the second end plate 18b. As Figure 2 and Figure 3 shown, with this connection, the first opening 44 and the second opening 46 are respectively closed by the first end plate 18a and the second end plate 18b. In addition, the first cylinder body 42 surrounds the single cell stack 14 of the fuel cell stack 10.

[0041] Figure 3 The state of connecting the first end plate 18a and the second end plate 18b to the first cylinder body 42 is shown. As described above, the outer edge end faces of the first end plate 18a and the second end plate 18b protrude from the outer edge end face of the single cell stack 14. Therefore, a space (gap 52) is formed between the outer wall of the single cell stack 14 and the inner wall of the first cylinder body 42.

[0042] At the uppermost part, i.e., the top wall, of the first cylinder body 42, there are a first insertion hole 54, a second insertion hole 56, and a third insertion hole 58 penetrating through the top wall. In the illustrated example, a gas sensor 60 is fitted into the first insertion hole 54. A fan 62 (diffusion device) for diffusion is fitted into the second insertion hole 56. An exhaust pipe 64 is provided in the third insertion hole 58. A sealing material (not shown) is sandwiched between the inner wall of the first insertion hole 54 and the gas sensor 60. Similarly, a sealing material (not shown) is also sandwiched between the inner wall of the second insertion hole 56 and the fan 62. A sealing material (not shown) is also sandwiched between the inner wall of the third insertion hole 58 and the exhaust pipe 64.

[0043] The gas sensor 60 and the exhaust pipe 64 may be provided in the same insertion hole. The gas sensor 60 may also be provided on the exhaust pipe 64. The opening diameter of the second insertion hole 56 is preferably sized to be able to insert the fan 62. Alternatively, after the fan 62 passes through the second insertion hole 56, a filler such as putty may be filled in the second insertion hole 56. It is preferred that the filler can be removed from the second insertion hole 56. In the case of performing a leak test under vacuum, it is not particularly necessary to provide the fan 62.

[0044] The detection result of the gas sensor 60 is displayed on an analysis device 66 such as a personal computer. In addition, the exhaust pipe 64 is connected to a vacuum pump 68. A valve 70 for stopping the exhaust is provided on the exhaust pipe 64.

[0045] In addition to the above-mentioned gas sensor 60, analysis device 66, fan 62, and vacuum pump 68, the airtight test device 40 further includes a panel 72. The panel 72 is a component for supplying or discharging inspection gas. The panel 72 is installed on the first end panel 18a.

[0046] The panel 72 is a single component. The panel 72 integrally has a cover part 74, an inspection gas supply pipe 76, and an inspection gas discharge pipe 78. The inspection gas supply pipe 76 and the inspection gas discharge pipe 78 are connected to the cover part 74. A screw insertion hole 80 is formed in the cover part 74. The position of the screw insertion hole 80 corresponds to the position of the threaded hole 24 formed in the first end panel 18a. The panel 72 and the first end panel 18a are connected by a connecting screw 20. That is, the connecting screw 20 passes through the screw insertion hole 80 and is connected to the threaded hole 24. Alternatively, instead of screw fixation, the cover part 74 may be pressed against the single cell stack 14 by a pressing device or the like to position the panel 72.

[0047] The cover part 74 is formed in a shape in which the portion facing the first end panel 18a is dug out in a quadrangular prism shape. Therefore, the cover part 74 has an outer peripheral part and a stepped part 81 surrounded by the outer peripheral part. The stepped part 81 is a concave part recessed away from the first end panel 18a. The inspection gas supply pipe 76 and the inspection gas discharge pipe 78 form openings at the stepped part 81. In addition, an inner chamber 82 is formed between the cover part 74 and the first end panel 18a due to the stepped part 81. A sealing member 84 prevents inspection gas from leaking from the inner chamber 82 to the outside of the first cylinder 42.

[0048] The cover part 74 covers the six communication holes 30a, 30b, 32a, 32b, 34a, and 34b formed in the first end panel 18a. Among them, according to the above description, the end face of the cover part 74 facing the first end panel 18a (the bottom surface of the concave stepped part 81) is separated from the six communication holes 30a, 30b, 32a, 32b, 34a, and 34b due to the step difference of the stepped part 81.

[0049] The inner chamber 82 of the cover part 74 is divided (partitioned) into two parts by a partition wall part 83. Thus, the inner chamber 82 has a first space 821 and a second space 822. The inspection gas supply pipe 76 communicates with the fuel gas discharge communication hole 30b, the oxidant gas supply communication hole 34a, and the cooling medium supply communication hole 32a via the first space 821 of the inner chamber 82. In addition, the inspection gas discharge pipe 78 communicates with the fuel gas supply communication hole 30a, the oxidant gas discharge communication hole 34b, and the cooling medium discharge communication hole 32b via the second space 822 of the inner chamber 82.

[0050] One end of the inspection gas supply pipe 76 is connected to an inspection gas supply source (e.g., a helium gas cylinder) via a pipe joint (not shown) and a supply pipeline. On the other hand, the other end of the inspection gas discharge pipe 78 is open to the atmosphere. Alternatively, the other end of the inspection gas discharge pipe 78 is connected to an inspection gas recovery device via a pipe joint (not shown) and a recovery pipeline. When the inspection gas discharge pipe 78 is connected to the inspection gas recovery device, the inspection gas can also be circulated and supplied from the inspection gas recovery device. A first on-off valve 86 is provided in the inspection gas supply pipe 76. A second on-off valve 88 is provided in the inspection gas discharge pipe 78.

[0051] In the above structure, inspection gas is supplied from the inspection gas supply pipe 76 to the fuel gas discharge communication hole 30b, the oxidant gas supply communication hole 34a, and the cooling medium supply communication hole 32a together. Inspection gas is discharged from the fuel gas supply communication hole 30a, the oxidant gas discharge communication hole 34b, and the cooling medium discharge communication hole 32b to the inspection gas discharge pipe 78 together.

[0052] Alternatively, instead, the branch supply pipes that are branched from the inspection gas supply pipe 76 into three branches can be individually connected to the fuel gas supply communication hole 30a (or the fuel gas discharge communication hole 30b), the oxidant gas supply communication hole 34a, and the cooling medium supply communication hole 32a. Similarly, branch discharge pipes can be individually connected to the fuel gas discharge communication hole 30b (or the fuel gas supply communication hole 30a), the oxidant gas discharge communication hole 34b, and the cooling medium discharge communication hole 32b, and the branch discharge pipes can be collectively connected to the inspection gas discharge pipe 78. In this case, on-off valves can be provided in the branch supply pipes and the branch discharge pipes respectively. According to this structure, it is possible to check whether there is a leak in the path from the fuel gas supply communication hole 30a to the fuel gas discharge communication hole 30b, for example. Similarly, it is possible to individually check whether there is a leak in the path from the oxidant gas supply communication hole 34a to the oxidant gas discharge communication hole 34b or in the path from the cooling medium supply communication hole 32a to the cooling medium discharge communication hole 32b. In addition, the above structure is not shown.

[0053] Next, with reference to Figure 4 the schematic flowchart shown, the leak test method (airtight test) according to the first embodiment will be described. In addition, hereinafter, the case where vacuum pumping is performed and the leak test is performed under vacuum is shown. However, in the case of simple implementation, it is also possible to omit vacuum pumping and perform the leak test at atmospheric pressure. In this case, it is not particularly necessary to provide the fan 62.

[0054] The leak test method according to the first embodiment has a cylinder installation step S1, a panel connection step S2, a vacuum pumping step S3, and a determination step S4. In addition, the cylinder installation step S1 and the panel connection step S2 are only different in order, and either step can be performed first. Here, the case where the cylinder installation step S1 is performed first is shown.

[0055] First, in the cylinder installation step S1, the fuel cell stack 10 is surrounded by the first cylinder 42. That is, the fuel cell stack 10 passes through the first opening 44 or the second opening 46 of the first cylinder 42. At this time, the position of the first end plate 18a corresponds to the position of the first opening 44, and the position of the second end plate 18b corresponds to the position of the second opening 46. Along with this, the screw insertion holes 50 formed in the first cylinder 42 overlap with the threaded holes 22 formed in the first end plate 18a and the second end plate 18b. After that, the operator passes the connection screw 20 through the screw insertion hole 50 and screws the connection screw 20 with the threaded hole 22. In addition, the sealing member 48 is provided in advance on the inner walls of the first opening 44 and the second opening 46.

[0056] Through the above screwing, the first end plate 18a is connected to the first cylinder 42 and the first opening 44 is closed. Similarly, the second end plate 18b is connected to the first cylinder 42 and the second opening 46 is closed. As a result, the fuel cell stack 10 is surrounded by the first cylinder 42. A gap 52 is formed between the outer wall of the single cell laminate 14 and the inner wall of the first cylinder 42.

[0057] Next, in the panel connection step S2, the panel 72 is connected to the first end plate 18a. That is, the connection screw 20 passes through the screw insertion hole 80 formed in the cover portion 74 of the panel 72. After that, the connection screw 20 is screwed with the threaded hole 24 formed in the first end plate 18a. The sealing member 84 is provided in advance on the panel 72.

[0058] As a result of the panel connection step S2, the fuel gas supply communication hole 30a, the fuel gas discharge communication hole 30b, the oxidant gas supply communication hole 34a, the oxidant gas discharge communication hole 34b, the cooling medium supply communication hole 32a, and the cooling medium discharge communication hole 32b are covered by the cover portion 74. In addition, an inner chamber 82 is formed by the cover portion 74 and the first end plate 18a.

[0059] After that, the gas sensor 60, the fan 62, and the exhaust pipe 64 are installed on the first cylinder 42. It is also possible to install the gas sensor 60, the fan 62, and the exhaust pipe 64 on the first cylinder 42 before performing the cylinder installation step S1. In any case, sealing materials are installed between the inner wall of the first insertion hole 54 and the gas sensor 60, between the inner wall of the second insertion hole 56 and the fan 62, and between the inner wall of the third insertion hole 58 and the exhaust pipe 64.

[0060] Moreover, after setting the first on-off valve 86 and the second on-off valve 88 to the closed state, the evacuation process S3 is performed. That is, the vacuum pump 68 is made to function and the exhaust stop valve 70 is set to the open state. As a result, the gas (atmosphere) present in the gap 52 between the outer wall of the single cell laminate 14 and the inner wall of the first cylinder 42 is attracted by the vacuum pump 68. That is, the gap 52 is evacuated. When there is a leak site in the fuel cell stack 10, the gas present inside the fuel cell stack 10 is also discharged at the same time.

[0061] After that, the exhaust stop valve 70 is set to the closed state and the fan 62 is made to function. In this state, the determination process S4 is performed using an inspection gas (e.g., helium). Specifically, the first on-off valve 86 is set to the open state, and the second on-off valve 88 is set to the open state. As a result, the inspection gas passes through the inspection gas supply pipe 76 and the inner chamber 82 (the first space 821), and flows into the interior of the fuel cell stack 10 from the fuel gas discharge communication hole 30b, the oxidant gas supply communication hole 34a, and the cooling medium supply communication hole 32a.

[0062] A part of the inspection gas flows through the fuel gas flow path and the oxidant gas flow path formed in the separator, respectively. Another part of the inspection gas flows through the cooling medium flow path formed between adjacent separators. The inspection gas is discharged to the inspection gas discharge pipe 78 through the second space 822 from the fuel gas supply communication hole 30a, the oxidant gas discharge communication hole 34b, and the cooling medium discharge communication hole 32b. As described above, the inspection gas flows inside the fuel cell stack 10. As a result, the gas inside the fuel cell stack 10 is replaced by the inspection gas.

[0063] After starting the introduction (flow) of the inspection gas and after a predetermined time, the second on-off valve 88 is switched to the closed state. Since the first on-off valve 86 remains in the open state, the pressure of the inspection gas inside the fuel cell stack 10 rises. After that, when the first on-off valve 86 is switched to the closed state, the inspection gas is sealed inside the fuel cell stack 10 at a predetermined pressure.

[0064] In the case where there is no leak site in the fuel cell stack 10, the inspection gas hardly leaks from the inside of the fuel cell stack 10 to the outside. Therefore, the concentration of the inspection gas in the gap 52 does not rise above a predetermined threshold value in a short time. In this case, no warning is displayed on the analysis device 66 either. Therefore, the operator can determine that "there is no leak site in the fuel cell stack 10".

[0065] In contrast, when there is a leakage site in the fuel cell stack 10, the inspection gas leaks from the fuel cell stack 10 into the gap 52. As the leakage site, for example, it is assumed to be the sealing structure between the MEA and the separator plate. Alternatively, as the leakage site, it is considered to be the sealing structure around the outer periphery of the communication holes 30a, 30b, 32a, 32b, 34a, and 34b. Here, the case where the inspection gas is helium is described. Helium is formed of single atoms. Therefore, the atomic radius of helium is small, and thus the inspection gas leaks in a relatively short time. As a result, the situation where leakage occurs can be identified quickly and with good accuracy. In addition, the inspection gas is not particularly limited to helium. Other preferred specific examples of the inspection gas include hydrogen, methane gas, nitrogen gas, etc.

[0066] When performing the leak test under vacuum, the fan 62 rotates inside the gap 52. Therefore, even if light helium is used as the inspection gas, the inspection gas easily moves from the leakage site toward the gas sensor 60. In addition, the gas other than the inspection gas is evacuated in advance in the gap 52, thus avoiding false detection caused by the gas other than the inspection gas. As a result, the gas sensor 60 can detect the inspection gas in a short time and with good accuracy. And the concentration of the inspection gas in the gap 52 is quickly obtained by the analysis device 66.

[0067] In this case, a warning is displayed on the analysis device 66. A warning sound is emitted as needed. Thereby, the operator can determine that "there is a leakage site in the fuel cell stack 10".

[0068] Thus, according to the first embodiment, it is not necessary to transport the fuel cell stack 10 to a dedicated device, and the leak test can be performed on-site. Moreover, a container sized to surround the fuel cell stack 10 can be used as the first cylinder 42. Therefore, an increase in the scale of the airtight test device 40 is avoided.

[0069] Moreover, when connecting the first cylinder 42 to the fuel cell stack 10, the threaded holes 22 and 24 formed in the first end plate 18a and the second end plate 18b are effectively utilized. After removing the first cylinder 42 from the fuel cell stack 10, predetermined components such as a protection panel are connected to the threaded holes 22 and 24. That is, the first cylinder 42 is connected to the fuel cell stack 10 via the threaded holes 22 and 24 formed for installing the predetermined components. Therefore, it is not necessary to separately provide a connecting portion for connecting the first cylinder 42 to the fuel cell stack 10. As a result, the shape or structure of the fuel cell stack 10 is prevented from becoming complicated.

[0070] The situation where leakage can be recognized is not only the case of leakage occurring from the hydrogen flow path (fuel gas supply communication hole 30a, fuel gas flow path, and fuel gas discharge communication hole 30b). Even when leakage occurs from the oxidant gas flow path (oxidant gas supply communication hole 34a, oxidant gas flow path, and oxidant gas discharge communication hole 34b) or the cooling medium flow path (cooling medium supply communication hole 32a, cooling medium flow path, and cooling medium discharge communication hole 32b), leakage can also be recognized. That is, in this case, regardless of which part is the leakage part, the existence of the leakage part can be sensed.

[0071] After the leakage test is performed as described above, the second on-off valve 88 is set to the open state. Thereby, the inspection gas is released to the atmosphere or recovered by the inspection gas recovery device. The recovered inspection gas can be supplied to the fuel cell stack 10 during the next leakage test.

[0072] For the fuel cell stack 10 determined to have "a leakage part", for example, processing such as further tightening a connecting rod (not shown) that connects the first end plate 18a and the second end plate 18b is performed. Or, sometimes the single cell laminate 14 is temporarily disassembled, and the leaking battery cell is replaced with a new battery cell. As described above, the leakage part is repaired.

[0073] Next, regarding the leakage test method according to the second embodiment, the case where water is used as the inspection liquid will be exemplified. In this case, the immersion test is performed using the Figure 5 shown immersion test device 100. In addition, for easy understanding, the same reference numerals are added to the structural elements corresponding to the structural elements of the first cylinder 42.

[0074] The immersion test device 100 includes a second cylinder 102 that surrounds the fuel cell stack 10. The second cylinder 102 is a container for performing the immersion test. As an example of the material of the second cylinder 102, a metal material such as aluminum alloy can be cited. However, it is preferable that the material of the second cylinder 102 is a resin material such as acrylic resin and is transparent as shown in the figure. The second cylinder 102 can be formed of a single member. As will be described later, the second cylinder 102 can also be formed by assembling a plurality of members with each other (refer to Figure 8 and Figure 9 ). The second cylinder 102 can also be formed by joining a plurality of plates to each other.

[0075] The case where the second cylinder 102 is composed of a single member is shown. In this case, the shape of the second cylinder 102 is substantially the same as the shape of the first cylinder 42. That is, the second cylinder 102 is a hollow body having a substantially rectangular cross section orthogonal to the longitudinal direction. At one end in the longitudinal direction of the second cylinder 102, a first opening 44 having an opening size corresponding to the outer dimension of the first end plate 18a is formed. At the other end in the longitudinal direction of the second cylinder 102, a second opening 46 having an opening size corresponding to the outer dimension of the second end plate 18b is formed. The fact that the inner wall of the first opening 44 and the outer edge end face of the first end plate 18a and the inner wall of the second opening 46 and the outer edge end face of the second end plate 18b are respectively sealed by the sealing member 48 is the same as in the first embodiment. In addition, at the longitudinal end of the second cylinder 102, a plurality of screw insertion holes 50 are formed at positions surrounding the first opening 44 and the second opening 46.

[0076] At the uppermost part, i.e., the top wall, of the second cylinder 102, a pipe insertion hole 104 and an opening 106 for exhaust are formed through. A water supply pipe 110 provided with a third on-off valve 108 passes through the pipe insertion hole 104. A water supply source (not shown) is connected to the water supply pipe 110. In addition, it is not particularly necessary to insert and install a sealing material between the inner wall of the pipe insertion hole 104 and the water supply pipe 110.

[0077] The immersion test device 100 further includes a panel 72 attached to the first end plate 18a. This panel 72 is the same as the panel 72 constituting the airtight test device 40. Therefore, the same reference numerals are given to the structural elements corresponding to those of the first embodiment, and the detailed description thereof is omitted.

[0078] Next, with reference to Figure 6 The schematic flowchart shown is used to explain the leak test method (immersion test) according to the second embodiment. The leak test method according to the second embodiment includes a cylinder mounting step S11, a panel connection step S12, a water introduction step S13, and a determination step S14. In addition, the order of the cylinder mounting step S11 and the panel connection step S12 is different, and either step can be performed first. Here, the case where the cylinder mounting step S11 is performed first is shown.

[0079] In the cylinder installation process S11, the same operations as those in the above-mentioned cylinder installation process S1 are performed, and the fuel cell stack 10 is surrounded by the second cylinder 102. That is, the fuel cell stack 10 is passed through the first opening 44 or the second opening 46 of the second cylinder 102, and the positions of the first end plate 18a and the second end plate 18b are respectively corresponding to the first opening 44 and the second opening 46. At this time, the screw insertion holes 50 formed in the second cylinder 102 overlap with the threaded holes 22 formed in the first end plate 18a and the second end plate 18b. Then, the operator passes the connecting screw 20 through the screw insertion hole 50 and screws the connecting screw 20 with the threaded hole 22. The sealing member 48 is previously provided on the inner walls of the first opening 44 and the second opening 46.

[0080] Through the above screwing, the first end plate 18a and the second end plate 18b are connected to the second cylinder 102. The first end plate 18a closes the first opening 44, and the second end plate 18b closes the second opening 46. As a result, the fuel cell stack 10 is surrounded by the second cylinder 102. In addition, a gap 52 is formed between the outer wall of the single cell laminate 14 and the inner wall of the second cylinder 102.

[0081] Next, in the panel connection process S12, the panel 72 is connected to the first end plate 18a. That is, the connecting screw 20 is passed through the screw insertion hole 80 formed in the panel 72, and the connecting screw 20 is screwed with the threaded hole 24 formed in the first end plate 18a. Through the panel connection process S12, the fuel gas supply communication hole 30a, the fuel gas discharge communication hole 30b, the oxidant gas supply communication hole 34a, the oxidant gas discharge communication hole 34b, the cooling medium supply communication hole 32a, and the cooling medium discharge communication hole 32b are covered by the panel 72. In addition, an inner chamber 82 is formed by the first end plate 18a and the panel 72.

[0082] After that, the water supply pipe 110 is inserted into the pipe insertion hole 104. The water supply pipe 110 may also be installed on the second cylinder 102 before performing the cylinder installation process S11.

[0083] Next, a water introduction step S13 is performed. Specifically, the third on-off valve 108 is set to the open state, whereby water W is introduced into the second cylinder 102 from the water supply source via the water supply pipe 110. The water W is stored in the gap 52, whereby the water level rises in the second cylinder 102. As a result, the water surface rises to the upper outer wall of the single cell laminate 14 to immerse the single cell laminate 14. In addition, only a space remains between the water surface and the top wall of the second cylinder 102. That is, in this case, only a gap 52 as a space remains between the upper outer wall of the single cell laminate 14 (cell unit 12) and the top wall (uppermost part) of the second cylinder 102. Further, during the rise of the water level, the gas (atmosphere) present in the gap 52 is discharged to the outside of the second cylinder 102 through the opening 106.

[0084] When the second cylinder 102 is transparent, the operator can easily confirm the water level by visual observation. When the water level rises to a predetermined height in the second cylinder 102, the operator sets the third on-off valve 108 to the closed state to stop the supply of water W. Alternatively, the third on-off valve 108 can also be automatically closed. In this case, a water level sensor and a control device such as a personal computer are provided. The water level sensor detects the situation where the water level reaches a predetermined height in the second cylinder 102. At this time, the control device performs control for closing the third on-off valve 108.

[0085] Next, in the same manner as in the first embodiment, an inspection gas is supplied into the fuel cell stack 10, and a determination step S14 is performed. Here, in the second embodiment, it is not particularly necessary to seal the inspection gas into the fuel cell stack 10. For example, both the first on-off valve 86 and the second on-off valve 88 can be set to the open state, and the inspection can be performed in a state where the inspection gas circulates in the fuel cell stack 10. Further, in the second embodiment, compressed air or compressed nitrogen can also be used as the inspection gas.

[0086] When the second cylinder 102 is transparent, the operator can easily confirm whether bubbles B are generated by visual observation. That is, when there is no leakage part in the fuel cell stack 10, almost no inspection gas leaks from the fuel cell stack 10 and sprays into the water W. Therefore, there is almost no situation where bubbles B are recognized in the water W. From this, it can be understood that the operator can determine that "there is no leakage part in the fuel cell stack 10" based on the situation where bubbles B are not visually recognized. Alternatively, it can also be determined that "there is no leakage part in the fuel cell stack 10" based on the situation where there is no inspection gas above a predetermined concentration in the gap 52 formed between the upper outer wall of the single cell laminate 14 and the top wall of the second cylinder 102.

[0087] On the contrary, in the case where there is a leakage site in the fuel cell stack 10, it is checked that gas leaks from the leakage site. In this case, the communication holes 30a, 30b, 32a, 32b, 34a, and 34b are covered by the panel 72. Therefore, the gas in the fuel cell stack 10 does not discharge from the communication holes 30a, 30b, 32a, 32b, 34a, and 34b, but leaks from the leakage site. As a result, as Figure 5 shown, bubbles B are generated in the water W. Based on the situation where the operator visually recognizes the bubbles B, it can be determined that "there is a leakage site in the fuel cell stack 10".

[0088] In this way, in the second embodiment, it is also unnecessary to carry the fuel cell stack 10 to a dedicated device, and the leakage test can be carried out in place. Moreover, a container having a size that can surround the fuel cell stack 10 can be used as the second cylinder 102. Therefore, there is no need for a large-scale water tank for immersing the entire fuel cell stack 10. That is, an increase in the scale of the immersion test device 100 is avoided.

[0089] Moreover, when connecting the second cylinder 102 to the fuel cell stack 10, the threaded holes 22 and 24 formed in the first end panel 18a and the second end panel 18b are effectively utilized. After removing the second cylinder 102 from the fuel cell stack 10, predetermined components such as a protection panel are connected to the threaded holes 22 and 24. That is, the second cylinder 102 is connected to the fuel cell stack 10 by means of the threaded holes 22 and 24 formed for installing the predetermined components. Therefore, there is no need to separately provide a connecting portion for connecting the second cylinder 102 to the fuel cell stack 10. Therefore, in the second embodiment, the shape or structure of the fuel cell stack 10 is also prevented from being complicated.

[0090] In addition, in the second embodiment, regardless of whether the leakage site is a hydrogen flow path, an oxidant gas flow path, or a cooling medium flow path, the presence of the leakage site can be detected.

[0091] In addition, in the second embodiment, as Figure 7 shown, an opaque third cylinder 120 can also be used. The third cylinder 120 is also a container for performing an immersion test. In this case, it is preferable to form a mounting hole 122 in the top wall of the third cylinder 120, and a bubble generation recognition device 124 is installed in the mounting hole 122. As a preferred specific example of the bubble generation recognition device 124, a camera or a sound collecting microphone can be cited. In this case, the immersion test device 100 is configured to include an analysis device 66 such as a personal computer.

[0092] In the structure using a camera, for example, based on processing an image, a situation where bubbles B are generated is detected. In the structure using a sound-collecting microphone, the sound emitted when bubbles B are generated is collected, and thereby the situation where bubbles B are generated is detected. In any case, a warning is displayed on the analysis device 66. A warning sound is emitted as needed. Thus, the operator can determine that "there is a leakage site in the fuel cell stack 10".

[0093] In the second embodiment, a liquid other than water can also be used.

[0094] Furthermore, the present invention is not limited to the above-described embodiments, and various structures can be adopted without departing from the gist of the present invention.

[0095] For example Figure 8 as shown, the cylinder 130 can also be composed of a plurality of members. In Figure 8 the insertion holes, pipe insertion through-holes, and other holes are omitted from the illustration. The same applies to those described later. The number of members is not particularly limited to Figure 9 and Figure 8 and Figure 9 shown as two. The number of members can also be three, four, or the like.

[0096] Figure 8 The cylinder 130 shown has a cylinder main body 132 and a closing plate 134. The cross-section of the cylinder main body 132 orthogonal to the longitudinal direction is substantially inverted in shape, with an opening formed at the lower part. The closing plate 134 closes the opening at the lower part of the cylinder main body 132. The closing plate 134 is connected to the cylinder main body 132. A bolt insertion hole 138 different from the screw insertion through-hole 50 is formed between the cylinder main body 132 and the closing plate 134. A bolt 136 for connecting the cylinder main body 132 and the closing plate 134 passes through the bolt insertion hole 138.

[0097] Figure 9 The cylinder 148 shown has a first L-shaped plate 144 and a second L-shaped plate 146. A first tab portion 140 and a second tab portion 142 are formed to protrude from the first L-shaped plate 144. The first tab portion 140 and the second tab portion 142 are connected to the second L-shaped plate 146. When the connection parts between the members are sufficiently sealed, the cylinders 130 and 148 can also be used as containers for performing an airtightness test.

[0098] In addition, the insulating plate 16a can be used as the first end structure member and the insulating plate 16b can be used as the second end structure member instead of the first end plate 18a and the second end plate 18b.

Claims

1. A method for leak testing a fuel cell stack, for checking whether there is a leak site in the fuel cell stack (10), the fuel cell stack (10) comprising: a single cell stack (14) formed by stacking a plurality of cell monomers (12); a first end plate (18a) located at one end of the single cell stack in the stacking direction; and a second end plate (18b) located at the other end of the single cell stack in the stacking direction. In the method for leak testing the fuel cell stack, it includes: A cylinder installation step (S1) of surrounding the fuel cell stack with a cylinder (42) having a first opening (44) and a second opening (46) formed at both ends respectively; And A determination step (S4), which is carried out after the cylinder installation step. In the cylinder installation step, the cylinder is connected to the first end plate and the second end plate, whereby the first end plate and the second end plate respectively close the first opening and the second opening. The cylinder extends from the first end plate to the second end plate, and a gap (52) is formed between the outer wall of the single cell stack and the inner wall of the cylinder. In the determination step, inspection gas is supplied to the inside of the fuel cell stack via the first end plate, and it is determined whether the inspection gas exists in the gap.

2. The method for leak testing a fuel cell stack according to claim 1, wherein The gap is formed between the upper outer walls of a plurality of the cell monomers and the uppermost part of the cylinder.

3. The method for leak testing a fuel cell stack according to claim 1, wherein After the cylinder installation step, a vacuum pumping step is included. In this vacuum pumping step, the gap is evacuated. The determination step is carried out after the vacuum pumping step. In the determination step, the concentration of the inspection gas in the gap is measured.

4. The method for leak testing a fuel cell stack according to claim 1, wherein The determination step is carried out while driving a diffusion device (62) in the gap.

5. The method for leak testing a fuel cell stack according to claim 1, wherein After the cylinder installation step, a liquid containment step is included. In the liquid containment step, a liquid (W) is contained in the gap. The determination step is carried out after the liquid containment step. In the determination step, it is determined whether the generation of bubbles (B) is identified in the liquid.

6. The method for leak testing a fuel cell stack according to claim 5, wherein At least a part of the cylinder is made transparent.

7. The method for leak testing a fuel cell stack according to claim 5, wherein A bubble generation identification device (124) is provided inside the cylinder, and the generation of bubbles is determined by this bubble generation identification device.

8. The method for leak testing a fuel cell stack according to claim 1, wherein The first end panel and the second end panel respectively have threaded holes (22, 24) for connecting a predetermined member. In the cylinder installation process, the first end panel and the second end panel are respectively connected to the cylinder by screws (20) screwed into the threaded holes.

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